Dan,
I'm not sure if you meant a written supplement, or an online program...
Here are a couple of Internet resources that look like they might be
useful.
1. S.O.S. Mathematics - Trigonometry
Learning units presented in worksheet format review the most
important results, techniques and formulas in college and
pre-college trigonometry.
http://www.sosmath.com/trig/trig.html
2. Tutornet - Live Interactive Tutoring
An interactive Web site featuring teacher-moderated chat rooms to
help students with tough homework problems in Algebra I, Geometry,
Algebra II, Trigonometry, Pre-Calculus, AP Calculus, Chemistry,
Physics, and Biology. Tutorials are scheduled in the afternoon hours
when students can access the site from school settings or their
homes, and in early evening hours, with hours tailored to the local
time of the students. As students log on, they select the subject
area that they want help with and are then placed in the classroom
with the fewest number of students at the time, greeted by a
"Netucator," and invited to type or write their question.
Tutornet.com allows students to print or save their work for later
reference. Subscription payments of $59.99/month for unlimited
access are made on-line using a secure credit card link.
http://www.tutornet.com/
3. Math Planet
A site for high school students featuring algebra, geometry, and
geometry concepts glossaries; crash courses on basic Algebra and
Geometry; an advanced course on Algebra and Trigonometry; a
customizable lesson plan based on individual level
http://library.thinkquest.org/16284/index_s.htm
4. Dave's short course in trigonometry
An introduction and a guide to trigonometry, with hints and answers
to exercises, and Java applets as illustrations, for which you'll
need a Java-enabled browser (Netscape 2 or later). Contents include
applications of trigonometry, angle measurement, chords, sines,
cosines, tangents and slope, the trigonometry of right triangles,
the trigonometric functions and their inverses, oblique triangles,
and a summary of trigonometric identities.
http://aleph0.clarku.edu/~djoyce/java/trig/
Hope that helps...
-Pat Ballew, for the Teacher2Teacher service